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Constraining the Bispectrum from Bouncing Cosmologies with Planck

Physical Review Letters 2023年第19期130卷 191002-191002页

作者： Bartjan van Tent Paola C. M. Delgado Ruth Durrer Université Paris-Saclay CNRS/IN2P3 IJCLab 91405 Orsay France Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University 30-348 Krakow Poland Department of Theoretical Physics Université de Genève Quai Ernest Ansermet 24 Genève 1211 Switzerland

Bouncing models of cosmology, as they arise, e.g., in loop quantum cosmology, can be followed by an inflationary phase and generate close-to-scale-invariant fluctuation spectra as observed in the cosmic microwave background (CMB). However, they are typically not Gaussian and also generate a bispectrum. These models can help to mitigate the large-scale anomalies of the CMB by considering substantial non-Gaussianities on very large scales, which decay exponentially on subhorizon scales. It was therefore thought that this non-Gaussianity would not be visible in observations, which can only probe subhorizon scales. We show that bouncing models with parameters such that they can significantly mitigate the large-scale anomalies of the CMB are excluded by the Planck data with high significance of, depending on the specific model, 5.4, 6.4, or 14 standard deviations.

关键词： Cosmic microwave background Quantum cosmology Quantum gravity

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Fuzzy Logic-Based Control of a Battery Energy Storage System to Mitigate Frequency Excursions in the Cuban Power System Caused by Electric Arc Furnaces

SSRN

引用

SSRN 2024年

作者： Domínguez, Julio Espinosa Serban, Ioan Breffe, Orlys Ernesto Torres Transilvania University of Brasov Department of Electrical Engineering and Applied Physics Faculty of Electrical Engineering and Computer Science Eroilor 29 Brasov500036 Romania Technological University of Havana Department of Electrical Engineering Faculty of Electrical Engineering Street 114 # 11901 e/ Ciclovía and Rotonda Havana19390 Cuba

This paper proposes an adaptive control for a battery energy storage system (BESS) using a fuzzy logic controller (FLC), specially designed to operate in parallel with an electric arc furnace (EAF) in the Cuban power system. The BESS control system was developed with considerations for the characteristics of the Cuban power system, the typical power demand profile of the EAF, and the lifetime of batteries. The primary goal is to mitigate the frequency excursions that currently occur during EAF operation, enabling the furnace to complete the smelting process without restrictions. Furthermore, the system aims to reduce battery overloading, thereby enhancing their lifetime. For this purpose, the BESS active power is managed by an adaptive compensator, governed by the FLC. Based on information coming from all the three components involved - power system frequency, furnace state and battery usage rate, the proposed FLC generates an optimum output to adjust the BESS behaviour. The performance of the proposed system was evaluated through simulations and experimental tests. The results demonstrate that using adaptive control applied to BESS can be an effective solution for steel plants connected to weakly-regulated power systems, such as the current Cuban power system. © 2024, The Authors. All rights reserved.

关键词： Fuzzy logic

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Vortex Counting and Velocimetry for Slitted Superconducting Thin Strips

引用

Physical Review applied 2023年第3期19卷 034098-034098页

作者： V.M. Bevz M.Yu. Mikhailov B. Budinská S. Lamb-Camarena S.O. Shpilinska A.V. Chumak M. Urbánek M. Arndt W. Lang O.V. Dobrovolskiy Physics Department V. Karazin Kharkiv National University Kharkiv 61022 Ukraine B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine Kharkiv 61103 Ukraine University of Vienna Faculty of Physics Vienna 1090 Austria University of Vienna Vienna Doctoral School in Physics Vienna 1090 Austria University of Vienna Faculty of Computer Science Vienna 1090 Austria CEITEC Brno University of Technology Brno 61200 Czech Republic

The maximal speed v∗ for magnetic flux quanta is determined by the energy relaxation of unpaired electrons and is thus essential for superconducting microstrip single-photon detectors (SMSPDs). However, the deduction of v∗ from the current-voltage (I-V) curves at zero magnetic field is hindered by the unknown number of vortices, nv, as a small number of fast-moving vortices can induce the same voltage as a large number of slow-moving ones. Here, we introduce an approach for the quantitative determination of nv and v∗. The idea is based on the Aslamazov and Larkin prediction of kinks in the I-V curves of wide and short superconducting constrictions when the number of fluxons crossing the constriction is increased by one. We realize such conditions in wide MoSi thin strips with slits milled by a focused ion beam and reveal quantum effects in a macroscopic system. By observing kinks in the I-V curves with increase of the transport current, we evidence a crossover from a single- to multifluxon dynamics and deduce v∗≃12 km/s. Our experimental observations are augmented with numerical modeling results, which reveal a transition from a vortex chain over a vortex jet to a vortex river with increase of nv and v. Our findings are essential for the development of one-dimensional and two-dimensional few-fluxon devices and provide a demanded approach for the deduction of maximal vortex velocities at the SMSPD operation conditions.

关键词： Superconductivity Vortex lattices

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Persistent currents in topological and trivial confinement in silicene

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Physical Review B 2020年第7期101卷 075408-075408页

作者： Piotr Jurkowski Bartłomiej Szafran AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 30-059 Kraków Poland

We consider states bound at the flip of the electric field in buckled silicene. Along the electric flip lines a topological confinement is formed with the orientation of the charge current and the resulting magnetic dipole moment determined by the valley index. We compare the topological confinement to the trivial one that is due to a local reduction of the vertical electric field but without energy gap inversion. For the latter the valley does not protect the orientation of the magnetic dipole moment from inversion by external magnetic field. We demonstrate that the topologically confined states can couple and form extended bonding or antibonding orbitals with the energy splitting influenced by the geometry and the external magnetic field.

关键词： Topological insulators 2-dimensional systems Quantum rings Silicene Topological materials Tight-binding model

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Quantum Optics Applications of Hexagonal Boron Nitride Defects

arXiv

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arXiv 2024年

作者： Çakan, Aslı Cholsuk, Chanaprom Gale, Angus Kianinia, Mehran Paçal, Serkan Ateş, Serkan Aharonovich, Igor Toth, Milos Vogl, Tobias Department of Computer Engineering TUM School of Computation Information and Technology Technical University of Munich Munich80333 Germany Munich80799 Germany Abbe Center of Photonics Institute of Applied Physics Friedrich Schiller University Jena Jena07745 Germany School of Mathematical and Physical Sciences Faculty of Science University of Technology Sydney UltimoNSW2007 Australia University of Technology Sydney UltimoNSW2007 Australia Department of Physics Izmir Institute of Technology Izmir35430 Turkey

Hexagonal boron nitride (hBN) has emerged as a compelling platform for both classical and quantum technologies. In particular, the past decade has witnessed a surge of novel ideas and developments, which may be overwhelming for newcomers to the field. This review provides an overview of the fundamental concepts and key applications of hBN, including quantum sensing, quantum key distribution, quantum computing, and quantum memory. Additionally, we highlight critical experimental and theoretical advances that have expanded the capabilities of hBN, in a cohesive and accessible manner. The objective is to equip readers with a comprehensive understanding of the diverse applications of hBN, and provide insights into ongoing research efforts. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum computers

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Dynamic Neural Potential Field: Online Trajectory Optimization in Presence of Moving Obstacles

arXiv

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arXiv 2024年

作者： Staroverov, Aleksey Alhaddad, Muhammad Narendra, Aditya Mironov, Konstantin Panov, Aleksandr The Artificial Intelligence Research Institute Moscow105064 Russia Federal Research Center "Computer Science and Control Moscow117312 Russia Center of Cognitive Modeling Moscow Institute of Physics and Technology Dolgoprudny141701 Russia Faculty of Electrical and Electronic Engineering University of Aleppo Syria Ufa University of Science and Technology Ufa450000 Russia

We address a task of local trajectory planning for the mobile robot in the presence of static and dynamic obstacles. Local trajectory is obtained as a numerical solution of the Model Predictive Control (MPC) problem. Collision avoidance may be provided by adding repulsive potential of the obstacles to the cost function of MPC. We develop an approach, where repulsive potential is estimated by the neural model. We propose and explore three possible strategies of handling dynamic obstacles. First, environment with dynamic obstacles is considered as a sequence of static environments. Second, the neural model predict a sequence of repulsive potential at once. Third, the neural model predict future repulsive potential step by step in autoregressive mode. We implement these strategies and compare it with CIAO* and MPPI using BenchMR framework. First two strategies showed higher performance than CIAO* and MPPI while preserving safety constraints. The third strategy was a bit slower, however it still satisfy time limits. We deploy our approach on Husky UGV mobile platform, which move through the office corridors under proposed MPC local trajectory planner. The code and trained models are available at https://***/CognitiveAISystems/ Dynamic-Neural-Potential-Field. © 2024, CC BY.

关键词： Cost functions

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Ageing of complex networks

引用

Physical Review E 2020年第4期102卷 042302-042302页

作者： Zdzislaw Burda Michalina Kotwica Krzysztof Malarz AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 30-059 Kraków Poland

Many real-world complex networks arise as a result of a competition between growth and rewiring processes. Usually the initial part of the evolution is dominated by growth while the later one rather by rewiring. The initial growth allows the network to reach a certain size while rewiring to optimize its function and topology. As a model example we consider tree networks which first grow in a stochastic process of node attachment and then age in a stochastic process of local topology changes. The ageing is implemented as a Markov process that preserves the node-degree distribution. We quantify differences between the initial and aged network topologies and study the dynamics of the evolution. We implement two versions of the ageing dynamics. One is based on reshuffling of leaves and the other on reshuffling of branches. The latter one generates much faster ageing due to nonlocal nature of changes.

关键词： Degree distributions Network evolution Network formation & growth

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Grain Stresses and Critical Resolved Shear Stresses in Duplex Steel Studied Using Neutron Diffraction and Crystallite Group Method

SSRN

引用

SSRN 2024年

作者： Baczmański, Andrzej Wroński, Sebastian François, Manuel Le Joncour, Léa Panicaud, Benoit Braham, Chedly Ludwik, Aleksandra Wierzbanowski, Krzysztof Klosek, Vincent AGH University of Kraków Faculty of Physics and Applied Computer Science al. Mickiewicza 30 Kraków30-059 Poland 12 rue Marie Curie Troyes10010 France PIMM 151 Bd de l’Hôpital 75013 Paris France CEA Laboratoire Léon Brillouin Gif-sur-Yvette91191 Cedex France

In this work, a new method for determining the critical resolved shear stress (CRSS) and stress concentration in polycrystalline grains was tested and applied to study the elastic-plastic properties of textured duplex steel. The methodology is based on in situ neutron diffraction measurements of lattice strains during tensile loading. The lattice deformations are measured for several hkl reflections and for different sample orientations with respect to the scattering vector. As a result, the full stress tensor for preferred texture orientations in function of applied stress has been determined using the crystallite group method (CGM). Knowing the experimental values of stresses, the stress concentration tensor is determined. The experimental data are then compared with self-consistent model calculations performed for groups of grains corresponding to the measured hkl reflections. The important advance of the proposed methodology consists in the possibility of estimating the CRSSs directly from measurements, without the use of any elastic-plastic *** the research carried out, on the basis of diffraction measurements, the evolution of grain stresses in preferred orientations in the ferritic and austenitic phases of the tested duplex steel was determined. Using these data, the evolution of the resolved shear stress (RSS) was analysed and, for the first time, CRSS values in both duplex phases were obtained directly from the experimental data. The final results also took into account the influence of initial stresses in the obtained material on the determined CRSSs. © 2024, The Authors. All rights reserved.

关键词： Neutron diffraction

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List covering of regular multigraphs with semi-edges

arXiv

引用

arXiv 2022年

作者： Bok, Jan Fiala, Jiří Jedličková, Nikola Kratochvíl, Jan Rzążewski, Pawel Computer Science Institute Faculty of Mathematics and Physics Charles University Prague Czech Republic Department of Applied Mathematics Faculty of Mathematics and Physics Charles University Prague Czech Republic Warsaw University of Technology Warsaw Poland University of Warsaw Warsaw Poland

In line with the recent development in topological graph theory, we are considering undirected graphs that are allowed to contain multiple edges, loops, and semi-edges. A graph is called simple if it contains no semi-edges, no loops, and no multiple edges. A graph covering projection, also known as a locally bijective homomorphism, is a mapping between vertices and edges of two graphs which preserves incidences and which is a local bijection on the edge-neighborhood of every vertex. This notion stems from topological graph theory, but has also found applications in combinatorics and theoretical computer science. It has been known that for every fixed simple regular graph H of valency greater than 2, deciding if an input graph covers H is NP-complete. Graphs with semi-edges have been considered in this context only recently and only partial results on the complexity of covering such graphs are known so far. In this paper we consider the list version of the problem, called List-H-Cover, where the vertices and edges of the input graph come with lists of admissible targets. Our main result reads that the List-H-Cover problem is NP-complete for every regular graph H of valency greater than 2 which contains at least one semi-simple vertex (i.e., a vertex which is incident with no loops, with no multiple edges and with at most one semi-edge). Using this result we show the NP-co/polytime dichotomy for the computational complexity of List-HCover for cubic graphs. Copyright © 2022, The Authors. All rights reserved.

关键词： Undirected graphs

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STAR-RIS-NOMA Assisted Power Constrained Covert Communication Systems

引用

IEEE Transactions on Vehicular technology 2025年

作者： Lei, Yuxin Huang, Gaojian Li, Xingwang Tian, Zhifa Mumtaz, Shahid Asif, Muhammad Henan Polytechnic University School of Physics and Electronic Information Engineering Jiaozuo454003 China City University of Macau Faculty of Data Science 999078 China Henan Polytechnic University School of Surveying and Land Information Engineering Jiaozuo454003 China Henan Polytechnic University School of Physics and Electronic Information Engineering Jiaozuo454099 China Southeast University National Mobile Communications Research Laboratory Nanjing210096 China Silesian University of Technology Department of Applied Informatics Gliwice Poland Department of Engineering Nottingham Trent University United Kingdom Jiangsu University School of Computer Science and Communication Engineering Zhenjiang China

In this paper, a covert communication system assisted by a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) in non-orthogonal multiple access (NOMA) networks is proposed. When the maximum channel power gain from the transmitter in the main network to the users in adjacent networks is smaller than the threshold, the transmitter sends the NOMA signals to the users with the assistance of STAR-RIS. Moreover, channel estimation errors and imperfect successive interference cancellation (SIC) are considered in the system analysis. To characterize the covert performance, the detection error probability (DEP) and the average minimum detection error probability (AMDEP) are first derived. Then, the closed-form solutions of the outage probability (OP) for the users are obtained. Finally, the maximum effective covert rate (ECR) subject to the covertness constraint and non-interruption constraint is studied. The numerical simulation results show that: 1) the detection performance of Willie (warden) deteriorates as the channel estimation errors increase;2) when the transmitter power exceeds the threshold, communication in the main network is interrupted;3) under a certain transmit power, the maximum ECR increases with the increasing of the number of STAR-RIS reflection elements. © 2025 IEEE.

关键词： Channel estimation

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